The aim of this project is to approach several answerable questions about the mode of synthesis and assembly of a multimeric eukaryotic protein, "fraction I protein" (ribulose-1, 5-bisphosphate carboxylase). This enzyme is responsible for CO2 fixation by chloroplasts. It has two types of subunits, one 55,000 daltons in molecular weight, the other considerably smaller -- between 12,000 and 24,000 daltons as estimated by a variety of methods. The large subunit has been shown to be synthesized in higher plant chloroplasts, while the small subunit has been shown to be synthesized on cytoplasmic polyribosomes outside the chloroplasts. The exact subcellular location of synthesis, the location and behavior of unassembled subunit pools, the aggregation states and solubility characteristics of the subunits, and their possible interactions with one another leading to assembly of complete enzyme, are being investigated.